Drastic Devaluation on MB and other luxury cars

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I am curious, I've owned a few used "luxury" cars. The main reason being, they devalue SO quickly.
I am curious as to why that is.
My car friends and I have decided that its due to a combination of reasons. The intended user wants something perfect and new, to show off. They do develope problems due to their complicated and "ahead of their time" systems. And, those systems cost 200 dollar an hour diagnostic fees and incredible parts prices if you get it fixed at the dealer, usually the only place that will work on them.
SO, if you have say, a Mercedes with 100k+ miles on it, it is expected it has more problems than anyone would put up with, at a cost of repair that would far outweigh the car.
Any other ideas?

This is my first Mercedes, but the car is put together so nice, and the bodies are so rust resistant, and the retail is so rediculously low and used parts are so cheap and plentiful, i can see making a hobby of buying broken mercedes and fixing them. Not for profit, but for fun and transportation.